Oscar-winning director Roman Polanski has broken his silence over the US bid to extradite him to face child sex charges, saying the case is based on a lie.

In a 900-word statement, Polanski says that he has asked "only to be treated fairly like anyone else".

He had previously told his lawyers to confine their comments to a bare minimum but now felt compelled to speak out.

"I can remain silent no longer because the request for my extradition addressed to the Swiss authorities is founded on a lie," Polanski said in the statement.

"I can no longer remain silent because the United States continues to demand my extradition more to serve me on a platter to the media of the world than to pronounce a judgment concerning which an agreement was reached 33 years ago."

Polanski is under house arrest in Switzerland after being arrested in Zurich in September on a US arrest warrant for having unlawful sex with a 13-year-old girl in 1977.

A California court quashed a bid last month by the 76-year-old to be tried in absentia, apparently exhausting his opportunities for appeals.

Polanski is alleged to have plied a girl called Samantha Geimer with champagne and drugs during a 1977 photo shoot at the Hollywood Hills home of actor Jack Nicholson before having sex with her despite her protests.

The director was initially charged with six felony counts, including rape and sodomy.

The charge was later reduced to unlawful sexual intercourse after a plea deal agreed in part to spare his victim the ordeal of a trial.

Polanski served 42 days at a secure unit undergoing psychiatric evaluation but fled the United States on the eve of his sentencing in 1978 amid fears that the judge planned to go back on the previously agreed plea deal.

In today's statement, Polanski insists that he has served the time agreed and claims to the contrary in the extradition warrant are false.

"The said request asserts that I fled in order to escape sentencing by the US judicial authorities, but under the plea bargaining process I had acknowledged the facts and returned to the United States in order to serve my sentence," he said.

Polanski claims that the efforts to bring him back to the US will cause further upset to Ms Geimer, who has publicly forgiven him.

"I can remain silent no longer because the California court has dismissed the victim's numerous requests that proceedings against me be dropped, once and for all, to spare her from further harassment every time this affair is raised once more," he said.

Polanski's flight from justice came after a string of hit films including Rosemary's Baby and Chinatown.

The director, whose then wife Sharon Tate was horrifically murdered by Charles Manson's "family" in 1969, won an Oscar for his 2002 film The Pianist but was unable to collect the award because of his fugitive status.

The Paris-based filmmaker says he has been forced to mortgage the apartment which has been his home for more than 30 years in order to meet his legal costs.

"Such are the facts I wished to put before you in the hope that Switzerland will recognise that there are no grounds for extradition and that I shall be able to find peace, be reunited with my family and live in freedom in my native land," he concluded.

Swiss officials said in February that a decision on whether to move forward with Polanski's extradition could not be made until the director had exhausted his US appeals.